In 2008 he finished second in the Tour de Romandie, 35 seconds behind Andreas Klöden, one of the world's leading riders. He avenged his loss by winning the Tour de Suisse by finishing 49 seconds ahead of Klöden and winning the mountain time trial to Klausen Pass. In his first Tour de France, he proved himself as an excellent climber among the world's greats, eventually finishing second in the youth competition, and 12th overall. After the Tour, Kreuziger was known to be one of the future riders to potentially win grand tours.

In 2009 he got back to the Tour de Romandie and finally succeeded in his attempt to win the race, getting also one stage victory. He added to this success by finishing in ninth place in the Tour de France.

In 2010 he won the Giro di Sardegna, finished third in Paris-Nice. Kreuziger's 9th overall in the Tour de France was a disappointment because it wasn't much of an improvement from his 9th place finish in the 2009 Tour (Though he would move into 8th after the Alberto Contador's stripped title). He then made the move from Liquigas-Doimo to Astana after five seasons with the Italian team.[3]

In 2011 Kreuziger won the mountains classification and a stage in the Giro del Trentino. He achieved a 4th place finish in the Liège-Bastogne-Liège by winning the sprint of the chasing group, almost half-a-minute behind winner Philippe Gilbert.[4] He then aimed for the Giro d'Italia. Kreuziger didn't quite had the uphill strength that Contador, Nibali, and Scarponi had, causing him to miss out on the podium. He ended up finishing 5th overall and he also won the young rider's classification.[5]

Kreuziger left Astana at the end of the 2012 season, and joined Saxo-Tinkoff on a three-year contract from the 2013 season onwards.[2] In April 2013 he won the Amstel Gold Race. He broke free of the lead group with 7 km (4.3 mi) to go and resisted to the peloton's surge on the Cauberg, taking a solo triumph.[9] Kreuziger worked with doping doctor Michele Ferrari according to former teammate Leonardo Bertagnolli.[10] When asked about the allegations after the Amstel Gold Race, Kreuziger refused to comment on the ties, saying he would address the topic after the Tour de Romandie.[11] He did and he admitted working with Ferrari from the autumn of 2006 through 2007 but that he did not use banned drugs.[12] After the Amstel Gold Race, Kreuziger finished 3rd in the Tour de Suisse after aiming to win it.

Despite riding the 2013 Tour to support Alberto Contador, Kreuziger left the Pyrenees 5th overall. After putting a solid time trial on stage 17, Kreuziger moved into the top three, moving ahead of Laurens ten Dam and Bauke Mollema. Despite moving into a high finish with Alberto Contador, Kreuziger slipped down to 5th overall after losing ground to Nairo Quintana and Joaquim Rodríguez in the alps.

In 2014, Kreuziger started his season finishing 8th in the Tour of Oman. He rode the Tirreno Adriatico in support of Alberto Contador though he finished 3rd overall with Contador winning the race. After, he rode through the Aredennes classics finishing in the top ten in the Fleche Wallonne and the Liege-Bastogne-Liege. He then finished 8th the Tour de Suisse.

In June 2014 Tinkoff-Saxo announced that Kreuziger was being temporarily suspended from racing after the UCI questioned abnormalities in his biological passport. The UCI had originally highlighted the problems in his biological data for the 2011 and 2012 seasons through a letter in June 2013, which Kreuziger had responded to in October 2013, even though the values did not get out of the biological passport range which determines what values the gained cyclist samples ought to have. The UCI subsequently followed this up in May 2014. This prevented Kreuziger from riding the Tour de France and Tour de Pologne.[13] In August 2014 the Court of Arbitration for Sport rejected an appeal by Kreuziger to allow him to start the 2014 Vuelta a España.[14] On 22 September, it was announced that the Czech Olympic Committee had cleared him of any anti-doping violation and that he was free to compete again.[15] The UCI and the World Anti-Doping Agency appealed against the decision to the Court of Arbitration for Sport in October 2014.[16] The case was dropped by both agencies on 5 June 2015.[17]